Coral bleaching is a phenomenon occurring in most coral reefs around the world (see NOAA map). Bleaching is a disease affecting the algae in coral reefs. These algae, known as Symbiodinium, have a symbiotic relationship with the coral and produce most of its food through photosynthesis whereby they convert solar energy into nutrients. They live within the coral and contribute to the reef structure as well as the reef’s color, the pigmentation serves the algae for photosynthesis. The coral is armed with hunting arms but without the algae hunting is not sufficient for the coral’s survival and after a period of starvation, it dies.
Coral reefs require constant water temperature and sunlight. They are the basis of most marine life systems and around them a rich ecological environment develops. Bleaching occurs when the algae die or leave their host. Their deaths indicate the decline of the ocean as an ecosystem. Coral bleaching is associated with either warming of the ocean water, an increase in acidity in the water composition and a turbidity that causes a decrease in the amount of sunlight in the water.
In the winter season, when the water temperature cools slightly, acceleration can renew the coral symbiosis and allow it to thrive again. But a few consecutive years of bleaching can lead to the death of the coral. The fear is that with the warming of the oceans, the effect of the algae will be greatly reduced and the entire reef will wane.
Coral reefs occupy about 3% of the ocean’s surface and hold a quarter of all species living at sea. About 10% of all coral reefs are dead, another 60% are in immediate danger.